[1] Democritus Univ Thrace, Dept Elect & Comp Engn, Power Syst Lab, GR-67100 Xanthi, Greece
[2] Aristotle Univ Thessaloniki, Sch Elect & Comp Engn, Power Syst Lab, GR-54124 Thessaloniki, Greece
[3] Univ Western Macedonia, Dept Elect & Comp Engn, GR-50100 Kozani, Greece
[4] Univ Strathclyde, Inst Energy & Environm, Dept Elect & Elect Engn, Glasgow G1 1QX, Lanark, Scotland